COURTESY OF DUKE UNIV. SCH. OF FOREST. 
FIGURE 98.—The Columbian timber beetle, Corthylus columbianus: A, adult; 
B, tunnels in the wood of a living white oak. Note that the entrance hole 
had healed over several years before the tree was cut. 
originating from the tunnels extend, often for considerable dis- 
tances, above and below them. These and the black-stained tunnels 
cause defects known variously as “grease spots,” “steamboats,” 
“spot worm,” “flag-worms,” and “black holes.” Damaged wood is 
rendered unfit for such uses as veneer, cooperage, or furniture. In 
southern Indiana, red and silver maple wood, which is highly 
valued in the furniture industry, is reduced in value by 38 percent 
(499). 
Corthylus punctatissimus (Zimm.), the pitted ambrosia beetle, 
occurs from southern Canada to Georgia and westward to the 
Great Plains. It breeds in a variety of trees and shrubs, such as 
maple, dogwood, American hornbeam, hop hornbeam, sassafras, 
rhododendron, and azalea. Young sugar maples are especially 
subject to damage, destructive infestations in them having been 
reported both in North Carolina and southern Canada. Cultivated 
rhododendrons and azaleas are also frequently attacked and 
killed. The adult is rather stout, cylindrical, dark brown or black, 
and about 4mm. long. The antennae and legs are rusty red-brown. 
The prothorax is longer than wide, roughly tuberculate in front, 
finely and sparsely punctured, shiny behind, and extends hood- 
like over the head. The elytra are strongly punctured but not in 
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